$num_domains = scalar @domains;

while ($num_domains > '0') { # Start Loopy Code

[blah]

    my $new_domain = shift @domains;

[blah]
 
    $num_domains = scalar @domains; # get the size of array

}

##</code><code>##

for ( 0 .. $#@domains ) {
    # do stuff
}

# or
for my $root_domain ( @domains ) {
    # blah
    push @domains, @new_domains;
}

##</code><code>##

my $root = 'd:/perl/';
my ( @dirs, @fails, @files);
@dirs = ( $root );
for my $dir ( @dirs ) {
    opendir DIR, $dir or die $!;#do { push @fails, $dir; next };
    while ( $_ = readdir DIR ) {
      next if -s "$dir/$_";
        do{ push @dirs, "$dir/$_";  next } if -d "$dir/$_" 
                                           and not m/^\.\.?$/;
        do{ push @files, "$dir/$_"; next } if -f "$dir/$_";
    }
}
print "$_\n" for @dirs;